Fibroblast lines will be established in tissue culture from patients with either schizophrenia or manic-depressive disease who have a family history of similar psychiatric illness. Diagnoses of patients and relatives will be determined by structured interview and review of records. The properties of monoamine oxidase (MAO), catechol-O-methyltransferase (COMT) and other enzymes and proteins of monoamine metabolism found in fibroblasts will be studied under standardized culture conditions. Enzyme activities will be examined both 1) in whole cells by determining the metabolites formed in culture and 2) in homogenates using standard enzyme assays. The effects of psychotropic drugs on metabolism will be tested both acutely and after longer culture of the drugs with the fibroblasts. Patients lines will be compared to controls. Fibroblasts enzyme activities will be compared to platelet MAO and red blood cell COMT activities.